Fan-powered edge-of-dock leveler

ABSTRACT

An edge-of-dock leveler includes a deck plate hingedly interconnected to a dock, a lip plate hingedly interconnected to the deck plate, an air pan mounted on the face of the dock to allow the air pan to rotate with respect to the dock, and a blower mounted on the air pan. The blower inflates an air bag that causes the air pan to rotate away from the dock face. A deck plate bearing is provided between the air pan and the deck plate, and causes the deck plate to rotate with the air pan. A locking arm hangs pendant from the lip plate until the deck plate has raised to a fully raised position, at which time the locking arm engages a bearing. The blower is turned off, allowing the air to escape the air bag, and the lip plate to extend as the air bag deflates.

This application is a continuation of U.S. application Ser. No.09/186,959, filed Nov. 5, 1998 now U.S. Pat. No. 6,098,227.

FIELD OF THE INVENTION

The present invention relates to edge-of-dock levelers.

BACKGROUND

Dock levelers are used to bridge the gap between a vehicle (e.g., atruck or a trailer) and a loading dock at which the vehicle is parkedfor unloading or loading. Dock levelers include pit-type dock levelers,which are mounted within a pit in the loading dock, and edge-of-docklevelers, which are mounted on the front edge of the loading dock.

Prior art edge-of-dock levelers include manual levelers wherein anoperator uses a lever to raise the edge-of-dock leveler above the levelof a vehicle bed parked adjacent to the dock. The leveler is thenlowered and a lip extends to engage the vehicle bed. These edge-of-docklevelers commonly include a spring that biases the edge-of-dock levelerupwardly to assist the operator when raising the leveler.

Other prior art edge-of-dock levelers include powered levelers. Forexample, one type of powered edge-of-dock leveler utilizes a hydraulicactuator to raise and lower the leveler. Another type of edge-of-dockleveler includes a fan or blower and an air bag. The air bag is inflatedwith the blower, raising the edge-of-dock leveler through a linkage.Examples of powered edge-of-dock levelers utilizing a blower and air bagare disclosed in U.S. Pat. Nos. 5,450,643 and 5,621,938.

SUMMARY

Several disadvantages have been identified in prior art dock levelersand edge-of-dock levelers. Hydraulic dock levelers are generally veryexpensive, and can require significant modification to the loading dock.Manual edge-of-dock levelers are controlled by an operator, and usuallyhave an upwardly-biased spring mechanism. The upward spring-biasutilized in manual edge-of-dock levelers often causes the edge-of-dockleveler to bounce as material handling devices are moved across them,creating a less stable device. Prior art fan-powered edge-of-docklevelers include relatively complex linkages, and therefore can be moredifficult to service.

The present invention provides an edge-of-dock leveler adapted to bemounted to the face of a loading dock. The leveler of the presentinvention includes a deck plate, a lip plate, and a removable air pan. Aretaining member is mounted on the dock face, and a portion of the airpan is received in the retaining member. The air pan is thereforeremovably mounted on the face of the loading dock for rotation withrespect to the dock face.

Mounted on the air pan is a blower. An air bag having a plurality of airlobes is mounted on one of the dock face and the air pan, and includesapertures through which the blower forces air into the bag. When the airbag is deflated, it hangs pendant between the loading dock face and theair pan. As the lobes are inflated by the blower, the lobes abut againstthe dock face and against the air pan, causing the air pan to pivotabout the retaining member away from the face of the dock. The air panincludes at least one deck plate bearing that abuts the underside of thedeck plate of the leveler. As the air pan is raised or lowered inresponse to inflation or deflation of the air bag, the air pan raisesand lowers the deck plate through the deck plate bearing. One or morebiasing members are provided to bias the deck plate and the air pan downtoward the dock face.

The edge-of-dock leveler of the present invention also includes a liplifter arm. The lip lifter arm hangs pendant from the lip plate as thedeck plate is raised. When the deck plate has been raised to apredetermined level, a notch in the lip lifter arm engages a bearingmounted on the loading dock. The blower is then turned off, allowing thedeck to settle downwardly under the influence of gravity and the biasingmembers, and forcing air out of the air lobes and through the blower.The blower fan provides resistance to the flow of air out of the airlobes, thereby causing the deck plate to settle at a controlled rate. Asthe deck plate is lowered, the lip lifter arm causes the lip plate toextend and come to rest on a portion of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a loading dock having the edge-of-dockleveler of the present invention mounted thereon.

FIG. 2 is a perspective view of the edge-of-dock leveler in a fullyinflated position.

FIG. 3 is a partially exploded view of the edge-of-dock leveler.

FIG. 4 is a cross-section view taken along line 4—4 in FIG. 1.

FIG. 5 is a cross-section view taken along line 5—5 in FIG. 4 with thedeck plate fully raised.

FIG. 6 is a cross-section view taken along line 5—5 in FIG. 4 showingthe air pan being removed from the dock face.

FIG. 7 is a cross-section view taken along line 7—7 in FIG. 5.

FIG. 8 is a cross-section view taken along line 8—8 in FIG. 4.

FIG. 9 is a cross-section view taken along line 9—9 in FIG. 8.

FIG. 10 is a cross-section view taken along line 10—10 in FIG. 9.

FIG. 11 is a cross-section view taken along line 11—11 in FIG. 4 showinga long spring mounting bolt.

FIG. 12 is a cross-section view taken along line 11—11 in FIG. 4 showinga short spring mounting bolt.

FIG. 13 is an exploded view of the air pan and air bag.

FIG. 14 is a cross-section view taken along line 14—14 in FIG. 13.

FIG. 15 is a cross-section view taken along line 15—15 in FIG. 4.

FIG. 16 is a cross-section view taken along line 15—15 in FIG. 4,showing the lip lifter arm engaging the bearing.

FIG. 17 is a cross-section view taken along line 15—15 in FIG. 4,showing the lip plate moving toward the extended position.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate a loading dock 10 for loading and unloading avehicle (not shown). The dock 10 generally includes a top portion havinga loading/unloading surface 14 over which forklifts and the like travel.The dock 10 also includes a dock face 22 to which an edge-of-dockleveler 26 is mounted.

The leveler 26 generally includes a pair of bumpers 28 for stopping thevehicle at a location spaced from the dock 10, a deck plate 30, and alip plate 34. The deck plate 30 includes ribs 38 that stiffen the deckplate 30. As seen in FIGS. 3, 5, and 6, the deck plate 30 is hingedlyinterconnected by way of a deck plate hinge 40 with a base plate orhinge plate 42 mounted on the dock face 22 via welds and concrete anchorbolts 62. The deck plate 30 is movable between a lowered or deflatedposition, shown in FIG. 1, and a raised or inflated position, shown inFIG. 2. When the deck plate 30 is in the lowered position, the deckplate 30 is supported by a support member 50 that extends away from eachof the bumpers 28 of the dock 10. When the deck plate 30 is in theraised position, the deck plate 30, and the rest of the leveler 26, willremain in the raised position until a force is applied to the deck plate30 causing the deck plate 30 to rotate, at which time gravity and abiasing force (explained below) will pull the deck plate 30 toward thelowered position.

The lip plate 34 is hingedly interconnected with the deck plate 30. Thelip plate 34 is movable relative to the deck plate between an extendedposition (FIGS. 1 and 17) and a pendant position (FIG. 15).

A pair of retaining members (FIGS. 3, 5, and 6), which in theillustrated embodiment are hook members 54, are mounted on a pair ofretaining plate members 58 that are mounted on the dock face 22 withconcrete anchor bolts 62. The hook members 54 are designed to detachablysupport an air pan 66, as described below in more detail.

The air pan 66 is generally L-shaped in profile (see FIGS. 5 and 6). Theair pan 66 includes an upper leg 70, a lower leg 74, a pair of gussetmembers 78 (FIGS. 2 and 3) extending between the legs 70, 74 to stiffenthe air pan 66, and end caps 82 connected to the ends of the upper andlower legs 70, 74. The upper leg 70, lower leg 74, and gusset members 78in the illustrated configuration are made from formed sheet metal thatis welded together. The end caps 82 include pivot bearings 86 that arereceived in the hook members 54 to detachably hold the air pan 66adjacent to the dock face 22 and to allow the air pan 66 to rotate withrespect to the dock face 22. The illustrated pivot bearings 86 comprisereplaceable bearings made of steel tubing with bronze bushings or otherbushing material.

The illustrated air pan 66 is approximately 55 inches long, and may beused with a base plate 42 between 66 inches and 84 inches long. Existingmanual edge-of-dock levelers may be converted to the leveler of thepresent invention regardless of the length of the base plate 42, deckplate 30, and lip plate 34 of the existing edge-of-dock leveler.

One or more (e.g., two) deck plate bearing assemblies 90 are provided onthe upper leg 70 of the air pan 66. The illustrated deck plate bearingassemblies 90 (see FIGS. 5, 6, and 15-17) include a bracket 94 mountedon the upper leg 70 at one end, and a ball bearing race or roller member98 mounted at an opposite end of the bracket 94. When the air pan 66 israised, as described below, the roller members 98 abut the underside ofthe deck plate 30 and causes the deck plate 30 to rotate about the deckplate hinge 40. The roller members 98 rotate with the pan 66 and rollalong the underside of the deck plate 30 to accommodate the relativemovement between the deck plate 30 and the air pan 66 caused by thenon-collinear pivot axes of the deck plate 30 and the air pan 66.

In this regard, the deck plate bearing assemblies 90 translate along theunderside of the deck plate 30 as the assemblies 90 rotate. As usedherein, “translate along” means that the portion of the deck platebearing assemblies 90 that contacts the deck plate 30 is free to travelalong a portion of the deck plate (e.g., the bearing assemblies 90 arenot pinned or fastened to the deck plate 30). Although the illustrateddeck plate bearing assemblies 90 include roller members 98 that rollalong the underside of the deck plate 30, alternative embodiments mayinclude members that slide along the underside of the deck plate 30, forexample. Also, in alternative embodiments, the deck plate 30 may beprovided with guide slots or rails in which the roller members 98 travelto ensure the roller members 98 translate along the deck plate 30 in asubstantially straight line.

In an alternative embodiment (not shown), the deck plate bearingassemblies 90 may be mounted on the lower leg 74. In this embodiment,the support 94 would be lengthened to allow the roller members 98 tocontact the underside of the deck plate 30, and the upper leg 70 wouldno longer be necessary.

A pair of reinforcing flanges 102 are welded or otherwise mounted acrossboth the base plate 42 and the retaining plate members 58 (FIGS. 3 and4). In operation, much of the weight of the deck plate 30 and lip plate34 is born by the air pan 66 and the hook members 54. Consequently, alarge bending moment is applied to each of the retaining plate members58. The reinforcing flanges 102 provided resistance to such bendingmoments.

A blower 106 is mounted on the air pan 66 between the upper and lowerlegs 70, 74. A power cord 110 extends from the blower 106, past one ofthe gussets 78, around one of the end caps 82, through a power cordbracket 114 (FIG. 4), through a power cord bushing 118 that is providedin one of the reinforcing flanges 102, and to a power source having aswitch (not shown). The cord 110 rotates approximately 90° each time thedeck plate 30 is rotated from the lowered position to the raisedposition. The power cord bushing 118 provides a low friction bearingsurface to prevent wear caused by the above rotation.

An air bag 122 is mounted on the air pan 66 between the lower leg 74 andthe dock face 22 (FIGS. 8, 13, and 14). The illustrated air bag 122includes several lobes that comprise PVC coated Nylon cloth that isfolded and secured in the illustrated configuration. As seen in FIGS. 13and 8, the air bag 122 includes a mounting portion 130 that issandwiched between a mounting member 134 (e.g., a strip of metal) andthe air pan 66 via fasteners 136 (e.g., bolts). In the deflatedcondition, the air bag hangs pendant between the dock face 22 and thelower leg 74 of the air pan 66. The illustrated air bag 122 includesfour lobes. The two front lobes are shorter than the rear lobes so thatthe front lobes clear a vehicle restraint (not shown) as they inflate.

Referring now to FIGS. 4, 9, 10, 13, and 14, the blower 106 is equippedwith an outlet 138 through which air is forced. The outlet 138 is influid communication with an aperture in the air pan 66 and with the airbag 122. The air bag 122 is provided with apertures 141 in each lobe toallow air to pass from one lobe into the next. Spacers 142 are disposedwithin each lobe adjacent the apertures 141. The spacers 142 arepreferably made of urethane or plastic, and are glued to the bag 122.The spacers 142 ensure that air from the blower 106 will enter eachlobe, and that air pressure in each lobe is equal to that in the otherlobes, thereby causing the lobes to fill relatively evenly. As the airbag 122 is inflated, air enters each of the lobes and the bag 122expands against both the lower leg 74 of the air pan 66 and the dockface 22. The pressurized air entering each lobe causes a pressure sealaround the perimeter so that air does not escape the air bag 122 in anysignificant quantity. The lobes may also be provided with additionalapertures 146 (FIG. 14) and spacers 150 to further ensure evendistribution of air within the air bag 122.

Referring now to FIGS. 11 and 12, a lower spring support 154 extendsfrom each bumper 28. The illustrated lower spring support 154 includesan L-shaped steel beam welded to a square beam. A bore is provided inthe L-shaped steel beam, allowing a spring mounting bolt 158 to passtherethrough. A biasing member, which in the illustrated embodiment is aspring 162, extends between the spring mounting bolt 158 and an upperspring support 166 secured to the deck plate 30. As the deck plate 30 ismoved from the lowered position to the raised position, the spring 162expands and provides a biasing force toward the lowered position. Thebiasing force causes the deck plate 30 to rotate about the hinge 40toward the lowered position. When the deck plate 30 is in the loweredposition shown in FIGS. 11 and 12, the lower end of the spring 162surrounds the shank portion of the spring mounting bolt 158. As the deckplate 30 is raised, the lower end of the spring 162 rises along theshank of the bolt 158 and eventually abuts the head of the bolt 158.This provides a “lost-motion” effect wherein the spring 162 does notprovide a downward biasing force until the lower end of the spring 162engages the bolt head. Thus, the amount of downward bias exerted by agiven spring 162 on the deck plate 30 can be controlled by the length ofthe spring mounting bolt 158.

FIG. 11 illustrates a long spring mounting bolt 158 while FIG. 12illustrates a relatively short spring mounting bolt 158. The long springmounting bolt 158 will cause a relatively small downward biasing forcewhen the deck plate 30 is in the raised position while the shorterspring mounting bolt 158 will cause a relatively large downward biasingforce when the deck plate 30 is in the raised position. For edge-of-docklevelers having very heavy deck plates 30 and lip plates 34, a shorterspring mounting bolt 158 is used to create a larger biasing force. Thelarger biasing force ensures that the heavier deck plate 30 and lipplate 34 will begin rotating toward the lowered position when the blower106 is turned off. A longer spring mounting bolt 158, creating a lowerbiasing force in the springs 162 when the deck plate 30 is in the raisedposition, may be used for lighter deck and lip plates 30, 34. In thisregard, a single spring 162 can be provided and the leveler 26 can becustomized by way of the spring mounting bolts 158, which are relativelyinexpensive and easily obtained.

A lip lifter arm 170 is pivotally connected to the underside of the lipplate 34. The lip lifter arm 170 includes a notch 174 at its distal end.A bearing 178 (FIGS. 4 and 15-17) is mounted on the base plate 42. Theillustrated bearing 178 includes a pin mounted between a pair of platesthat include one of the reinforcing flanges 102. When the deck plate 30is in the lowered position, and there is no vehicle present at the dock10, the lip lifter arm 170 hangs downward in a pendant position (FIG.15). As the deck plate 30 approaches the raised position, the lip lifterarm 170 swings toward the bearing 178, and the notch 174 in the liplifter arm 170 receives the bearing 178 (FIG. 16).

When the deck plate 30 has reached the raised position, the blower 106is turned off, and the deck plate 30 is pulled down toward the loweredposition by the springs 162 and by gravity. As the deck plate 30 ispulled down toward the lowered position, air in the bag 122 is expelledthrough the blower 106. A fan or impeller (not shown) in the blower 106provides resistance to the air flow, and causes the deck plate 30 tolower in a controlled manner. As the deck plate 30 lowers, the lip plate34 is extended due to the lip lifter arm's 170 engagement with thebearing 178 (FIG. 17). The deck plate 30 and lip plate 34 cease to lowerwhen the lip plate 34 comes to rest on the vehicle, at which time thelip lifter arm 170 disengages the bearing 178.

After cargo has been loaded or unloaded from the vehicle, the blower 106is again turned on, and the air bag 122 is inflated until the deck plate30 is partially raised and the lip plate 34 has disengaged the vehicle.Then the blower 106 is turned off, allowing the deck plate 30 to returnto the lowered position with the lip plate 34 and lip lifter arm 170hanging in the pendant position (FIG. 15).

As illustrated in FIG. 3, the deck plate 30 may also be maintained inthe raised position while the other components of the edge-of-dockleveler 26 are being serviced. To maintain the deck plate 30 in theraised position, the spring mounting bolts 158 are first detached fromthe lower spring support 154 to allow the springs 162 and springmounting bolts 158 to hang freely from the deck plate 30. Then the airbag 122 is inflated to raise the deck plate 30 to the raised position.The deck plate 30 will stay in the raised position until the deck plate30 is rotated a predetermined amount toward the lowered position. Whenthe deck plate 30 is in the raised position, the air pan 66 may beremoved (FIGS. 3 and 6), and easy access is provided to the othercomponents of the edge-of-dock leveler 26.

Although particular embodiments of the present invention have been shownand described, other alternative embodiments will be apparent to thoseskilled in the art and are within the intended scope of the presentinvention. Thus, the present invention is to be limited only by thefollowing claims.

What is claimed is:
 1. A dock leveler for use on a loading dock, thedock leveler comprising: a deck plate movable between a raised positionand a lowered position, wherein said deck plate is beyond a verticalposition when in said raised position; at least one biasing member forbiasing said deck plate toward said lowered position when said deckplate is in said raised position; and an air bag positioned under saiddeck plate and inflatable to move said deck plate from said loweredposition to said raised position against said biasing member.
 2. Thedock leveler of claim 1, wherein said biasing member comprises a spring.3. The dock leveler of claim 1, wherein said biasing member includes alost motion member, said lost motion member allowing said deck plate tomove a distance from said lowered position prior to said biasing membercreating a biasing force toward said lowered position.
 4. The dockleveler of claim 3, wherein said biasing member comprises a spring, andwherein said lost motion member includes a shank portion and a headportion, a portion of said spring sliding along said shank portiontoward said head portion when said deck plate is moved from said loweredposition toward said raised position, said spring creating said biasingforce upon movement of said deck plate toward said raised position aftersaid spring abuts said head portion.
 5. The dock leveler of claim 1,wherein said deck plate is hingedly interconnected with the loadingdock.